AuthorTopic: Rebuilding a Sherwood Pump (Read 3565 times)

Jim : Would love to help you, but I just set out for 6 weeks of sailing. My article is on my home computer, not the laptop I have with me. You’ll have to get out your past copy of the Mainsheet tech notes (2 or 3 issues back?).If you don’t receive the Mainsheet, Stu Jackson will be more than happy to sign you up.

Maybe Jack might send you a copy of the article if he still has it on his computer. Hope this helps

Here's the story & pictures, thanks to Jack. Rebuilding an Oberdorfer is in the wiki under Engine.

The pictures are jpeg and I have to convert them to jpg to post them. I just Googled "convert jpeg to jpg and found a handy online site to do just that.

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REBUILDING A SHERWOOD RAW WATER PUMP

The model of the Sherwood that I rebuilt is the G908. It has a cast bronze housing for the impeller cavity with the threaded ”inlet/outlet” on the top of the housing (no front plate). This is the standard pump on the M35BC and M25XPB engines. I only rebuilt the “water” side of the pump and as with an Oberdoffer pump, I’ve found that the “oil” side of the pump seldom leaks.

The water side seal on the pump consists of two ceramic discs pressing against each other. One disc rotates with the impeller and shaft, while the other one is stationary. The stationary disc is also spring loaded to keep pressure against the rotating disc to form the “seal”, keeping the water inside the pump housing. There is a copper snap-ring that is inserted in the shaft to hold the compressed discs in place.

I found that my “water snap-ring” was almost completely eroded. That snap-ring must be removed to separate the two discs. The top disc and a brass washer slide right off the shaft when the snap ring is removed. I placed the pump body in a vice and took a flat tip screwdriver pressing in the spring assembly. I removed what was left of the snap-ring with a long nose vice grips and pulled it out. You’ll need to take the end of a flat tip screwdriver and pry up the edges of the bottom of the old spring assembly. Then the spring assembly is easily pulled out and you can see the larger snap-ring that holds the oil seal in-place. Clean the inside thoroughly.

To reassemble, put the pump body between two pieces of 2x4 or drill a ¾” hole in a 2x4, so the pump body will set level with the shaft extending in between the 2xs or in the hole. Then take the new spring assembly (DEPCO# SH 12859) and coat the inside mating side with #1 Permatex. Do not use #2 Permatex as it’s too soft, because you need a hard seal! Press or tap the assembly into position. I used a 1”PVC joiner because it had the correct diameter and only cost $1. Then clean any excess Permatex that may squirt out. Coat the shaft with some silicone spray and slide on the mating ceramic disc (DEPCO #SH 18806) and brass washer. You will need a snap-ring tool to open the new snap-ring. With one hand press down and hold the two ceramic discs below the snap-ring groove in the stainless shaft and with the other hand slide the snap-ring into place.

One of the Sherwood pumps’ weak points is that the snap-rings that hold the “water side” seals and the “oil side” seals in place are made of copper. The oil side isn’t a problem as the oil keeps the snap-ring from corrosion, but in a salt water environment the water side snap-ring will slowly corrode as salt water is pumped. I changed my 5/8” exterior water side copper snap-ring to a stainless one (Prospect Fastener Corp #SHI 5/8”). Those older Catalina readers may remember when the heads made by JAPSCO (late 1980s) had a copper “C” clip on the bottom of the hand pump assembly holding everything together. That copper clip corroded rendering the pump useless and JAPSCO later changed to a stainless clip. I’ve passed this SS snap-ring information on to DEPCO.

I’m not going to compare all of the pros/cons of a Sherwood vs. an Oberdoffer pump, but I will mention a few of the less talked about aspects. I found that when you have a Sherwood pump and it’s leaking water that you can remove the bronze pump housing (impeller inside) leaving the water hoses attached and just move it to one side. Then remove the pump body from the engine and replace it with a rebuilt pump body and reattach the bronze pump housing w/impeller. No unscrewing brass elbows or water hoses. I also see that the inside brass plate that the impeller rides on can be reversed if one side is worn or scored.

My drive belt installation is not captive by the inlet water hose as most of the C34 Mk II factory installations are. There is a simple fix that Bill Nuttall “Irish Lady” #1244 wrote up in past Tech Notes – cut the inlet raw water hose and install 5/8” garden hose male and female fittings! Then to change the belt, disconnect the fittings, change the belt and reconnect the fittings – simple as that!!

I’m sure that the procedures that I used for my G908 Sherwood pump are basically the same as for the other Sherwood’s that have the bronze faceplate held in place by 4 screws. Those older model pumps (Model # G902) are used on some of the M25XP and M35 engines, I’ll guess the parts are probably different?

I might also add that DEPCO Pump Company (800-445-1656) has a service department (beside parts) and they charge a flat rate labor charge of $37.95 to rebuild a pump, if you don’t want to rebuild it yourself. I also discovered that the G908 pump is a proprietary Sherwood pump solely manufactured for Westerbeke. That means all G908 pumps can only be purchased from or thru a Westerbeke dealer!